Security and privacy represent important issues in modern communication over fixed or mobile wireless networks. The classical protocol of communication stack recommended by OSI is continuously changed to accommodate new routing techniques. For instance, routing can not only be implemented in the third (routing) layer of communication protocols but also in the second (link) layer, as proposed by Mesh Networks, or at upper layers (i.e. application layer), as proposed by peer-to-peer networks. By providing intermediate nodes access to data packets, network communication is inherently insecure. In seamless mobility scenarios, nodes can act in an ad-hoc manner as routers for packets sent by others. In certain scenarios, such nodes can even act as bridges between different networks. Such networks can have different access restrictions to the fields of the packets forwarded. Moreover, nodes acting as bridges might need rights to access more packet fields than regular routing nodes.